Solved it pretty quickly, following a rejoinder in the forums by VeryMisunderstood urging me to keep tracking down the conflicting module.

I was hoping I wouldn't have to track the bad boy down, both because of a) the nuisance factor, and b) fear of what I might find. Oh well, nothing to do but roll up the sleeves and de-conflict.

The first fear didn't turn out so bad. My old-school (pre-OS X) Mac training came in handy: it was just like pinning down an extension conflict. And I found the user-contrib module that clashed with Polls.

No, I'm not talking about Florida, or any of the latest voting machine fiascos. I mean the plain old Drupal core Poll module.

I used to have polls working nicely on another site. One day, they stopped working. Go to a poll, and... no content on the page. Just a title, then skip right to comments or trackbacks or whatever ends the page. Everything's there but a poll.

That site was upgraded from an old 4.x installation, and who knows what I may have messed up along the way. I forgot about it.